[vortex] causes 3c905c jitter ???
Tue Dec 18 17:41:01 2001
On Tue, 18 Dec 2001, Stefan Doehla wrote:
> I have here a realtime application with RTLinux. It seemed to me that
> some PCI cards vblock from time to time the PCI bus. E.g. video cards
> tend to use the pci_retry feature of the PCI spec -> PCI bus is locked
> for some microseconds. This problem was solved with a downgrade to XFree
This is a know problem with video cards. Since a few percent difference
is considered a major advantage in the gaming market, the hardware tends
to cheat on the specs and be bandwidth hogs. NICs are a much less
agressive market -- people are more realistic about performance and
> To my problem: XForwarding and some other network stuff (which should be
> used later in conjunction with the realtime programs) causes also
> jitter. It seems like the softwareside is okay.
> It looks like only outgoing traffic causes problems ...
> Can the 3com networkcard lock the PCI bus for some microseconds? Uses it
> a fifo that's not checked before writing (due to performance gains)?
What chip, and what driver version?
You can change various settings to limit the PCI burst size, but I don't
know what you are seeing that's a problem.
Donald Becker firstname.lastname@example.org
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Second Generation Beowulf Clusters
Annapolis MD 21403 410-990-9993